Basic mechanisms of the secretory process are studied in cells of the rat pancreas, salivary and lacrimal glands. Techniques utilized include light and electron microscopy, cytochemistry, radioautography, and biochemical determination of enzyme and cyclic nucleotide levels. Major areas of investigation are: (1) the role of the Golgi apparatus and GERL in secretory granule formation; (2) the structure and function of GERL and cyclic nucleotide levels in secretory cells of the beige mouse, a homologue of the human Chediak-Higashi syndrome; (3) the role of lysosomes in the intracellular degradation of secretory material; (4) the fate of endocytic vesicles formed during the removal of membrane from the luminal plasmalemma in vivo; (5) the route of access of extracellular material to the saliva; and (6) the structure, cytochemistry and distribution of peroxisomes.